Aibcrafsi



Nov. 1, 1938. J. M. GWINN, JR 'Re.'2

' AIRCRAFT ori inal Filed Jan. 24, 1955 HQL Z1 10 W1- y; Fig.5.

EXTERNAL DIHEDRAL ANGLES 1 F1 .8. a 139.6 4% hb v 20 INVENTOR ATTORNEYS dosep pMxiwinmJt,

Reissued Nov. l, 1938 uuirso STATES e. racer.

PATENT osic Joseph M. Gwinn. Jr., Buffalo, N. Y.

Original No. 2,030,631, dated February 11, 1936,

Serial No. 3,306, January 24, 1935. Application for reissue February 5, 193 8, Serial No.

the upper and lower surfaces of the two sections adjacent the hinge location being so provided and arranged as to afford a comparatively low section drag throughout an effective range of camber adjustment and to afford a comparatively high section. drag when the camber isadjusted above or below said effective range.

Another object of the invention is the pro-. vision of an aerofoil embodying a main fixed front section and a pivotally movable rear section, both of constant contour, the external dihedral angles between the. sections as defined by lines tangent to the contours of said sections adjacent the point of pivotal connection being ofa summed value'that is substantially less than 360 degrees, so as to provide for no convex discontinuity of the aerofoil surface throughout a substantial range of positions of the rear section.

Other objects and advantages of the invention will be apparent from the following description, the appended claims, and the accompanying drawing, in which,-

Fig. 1 shows atransverse section through an aerofoil embodying the present invention, the rear adjustable section being shown in a mid position;

Figs. 2, 3 and 4 are sectional views of the aerofoil surface with the rear section shown in raised low drag,'.lowered low drag, and high drag positions, respectively;

Fig. 5 is an enlarged detail through the aerofoil shown in Fig. l; 4 I

Fig. 6 is a top plan view of an airplane pro vided with an aerofoil surface of the present invention; 4

Fig. 'l is a sectional view showing a modified form of flap section; and

Fig. 8 is a sectional view showing a modified form of hinge connection.

Referring more particularly to the drawing, in generally designates an aerofoil, such as 'the sustaining, controlling or'tail surface of an airplane or the like. This aerofoil surface embodies a plurality of relatively movable sections pivotally connected or hinged together and providing for changes in the effective camber. As herein 10'Claims. (01. 244-42) shown, the invention isadapted and illustrated as applied to the main sustaining surface of the airplane, the front. section II being fixed to the airplane body or fuselage l2, while the rear section l3, which constitutes an aileron or wing fiap of any desired length, is hinged adajacent its forward edge to the rear portion of the front section II and controlled by any suitable means by the operator while the aircraft is" in flight for the regulation of the efiectivecamber and for stabilizing and steering purposes. While the sections H and I3 constitute the main sustaining surface of the aircraft in the form of the invention as herein described for purposes of illustratiop, it will be apparent that theinvention is not limited to surfaces which are horizontal or which are provided near the center of gravity of the aircraft to operate as the main sustaining surface.

The usual wing fiap or wing flap type of aileron of an airplane has ordinarily been so constructed and designed that its upper surface adjacent the hinge location is substantially in smooth continuation of the curvature of the upper surface of the fixed front portion of the wing, while at the same time the lower surface 1 of the flap or aileron is substantially in smooth continuation of the lower surface of the fixed portion of the wing. with this arrangement, as soon as the flap (or aileron) is moved downwardly from its normal position a break occurs in the convexcontinuity of the upper surface of the wing. As the "air follows with difliculty a surface having a line of convex discontinuity extending across the direction of air flow, said convex discontinuity causes the air fiow to leave the airfoil surface at said discontinuity, producing turbulent flow with a great increase in drag. With a flap this is quite a disadvantage. especially at the time of take-off from the ground, when low drag is a desirable factor.- While in fiight, high drag on the aileron which is down is undesired. g

In accordance with the present invention, the disadvantages of the prior arrangement have been effectively overcome in a' simple construction embodying a plurality of relatively movable sections each of constant or fixed contour. Since the sections are of fixed form or contour they may be made quite light in weight and of strong and simple construction. The front section ll of the sustaining surface as herein shown constitutes a main fixed front section of suitable contour defined by the upper and lower surfaces It and I5 respectively, whichare suitably seall leslrsd manner to transversely exof consine compared oi mover.

e thickness and vertical depth as its overall length in the direction as shown, the thickness ratio,- that is vertical depth divided by total length, This figure, however,

or minimum value. But with a comparatively thick surface section appreciable difference in augularity oi the upper and lower surfaces just ahead and behind the hinge location may be provided for even though the chordwise length of the movable section is quite long. The rear portion of the fixed Section N, as shown in Fig-1, tapers rearwardly although at the rear of thissection adjacent the aileron or wing flap hinge ill the upper and lower surfaces it and ii are usually spaced apart a substantial distance.

The rear movable section 53, which is preferably considerably shorter in chord length than the length of the section ll, as herein shown in Figs.

1 to 6 inclusive, comprises upper and lower surfaces is and i 5 supported on transversely extending supporting means 20, the parts [8 and 20 being hinged together along the hinge axis l'i 'so that the section i3 can be moved or adjusted to dlfferent angles. As will be apparent from Figs. 1 and 5, the included angle b between the upper and lower surfaces of the rear section I3 at or just to the rear of the hinge location is substantially mathematically less than the included angle a between the upper and lower surfaces of the fixed section ii just at or ahead of the hinge position. in its midpositlon he rear section 53 is approximately in continuation of the median line 2| of the front section, as shown in Fig. 1. In this position, there is no large break in the curvature continuityof either the upper or lower surface of the wing adjacent the hinge location and, what is also relatively important, there is no convex discontinuity in either surface of the wing so that the resistance or drag of the sections H and I3 is relatively small. This drag is still small even in Fig. 2, is one for low camber while the position indicated d and shown" in Fig. 3 is one for high lift, but in both of these positions and throughout the angular range between these two positions which corresponds to the usual range of eflective working for control operations while in flight, the section or parasite drag is quite small.

In the position 0 the lower surface of the entire aeroioil is gradually curvedand of continuous convex form ,while the upper surface is without convex discontinuity, that is the exterior angle between the rear upper portion of the fixed section ii and the upper forward part of the section is not greater than degrees. It will be served from Fig. 3 that this is also true of the upper sin-lace when the section I3 is in the low drag high lift position d, and in this position there is also no convex discontinuity in the lower sur z'ace. The section ll'may therefore be moved through a rather wide range of positions including the positions illustrated at c and d and intermediate positions without substantially changing the drag from its low initial value. When used as wing flaps, which are simultaneouslymoved downwardly in the same direction under the control the section II represented by the aosoi of the operator, the drag may therefore be inept quite low while the lift is high, at the time of take-off from the ground, a condition unattainable in the usual form of wing flap construction. It will be apparent that the results obtained by the invention will depend uponv the difference between the angular positions c and d (Figs. 2 and 3). Extensive flight and wind tunnel tests have proven that an angular difference of the order of 16 degrees, as is illustrated in the drawing herein, produces a preferred balance of advantages and disadvantages for small, low speedairplanes. 0bviously, however, this angular diff erenoe may in some cases be considerably greater, and asaircrait sizesand speeds increase the preferred angular difference will become smaller because the available angular difference is a tunetion of airfoil thickness ratio and the drag disadvantage of' thick airfoils increases rapidly with increased speed. Therefore, the invention contemplates a wide range of substantial angular diiferences including ranges as low as say 8 degrees of angular diflerence wherein the available low drag range may be still suitable for some types of aircraft; and as used in this specification and the claims, the term "substantial asiappliedto angular differences is intended to define an angular difference coming within the above described range.

Under flying conditions when the flap is used as an aileron, it may sometimes be desirable or necessary to move the section 13 higher than position 0 to position e as shown in Fig. 4 in dotted lines, where a convex discontinuity in the under surface occurs. In this position the drag is substantially increased, which increase in drag is of great value on the side of the airplane of the upwardly moved aileron. when it isdesired to position the section I3 for landing purposes, it may be moved down to the position shown in full lines in Fig. 4 and as represented by the letter I, to provide a high lift, serving by reason of the high drag to steepen the angle of glide and to shorten the lengthof run along the ground.

The flap or aileron l3 may, if desired, have I parallel top and bottom surfaces, as shown in Fig.

7 in which the flap or aileron is constructed, for

high drag position, thus.

example, of a single thickness'of plywood or metal, hinged to the rear part of the fixed section II by a. hinge i'l' provided on the lower surface.

The hinge may be of any desirable form, the

modified form of binge shown in Fig. 8 comprising a strap type hinge "a connecting the tube 20a at the front of the flap "a. to the rear end of the fixed section Ila.

As stated hereinabove, the included angle b betweentlre upper and lower surfaces of the rear section l3'is--'mathematically less than the ineluded angle a between the upper and lower surfaces of the fixed section H. It will be apparent, however, that the parts may be so relatively proportioned and designed that the section I 3 may be constructed with its upper and lower surface contours both of convex form, thus providing a lensshaped section. In such case the angle 3) between contour-tan. .ntial lines adjacent the point of pivot may he geometrically greater than the included angle a while still being mathematically less because oi the change of the mathematical sign thereof. in either the external dihedral angles between the sections, as defined by lines tangent to the contours adjacentthe point of pivot, will have a summed value substantially of less than degrees.

' rapidly with flap An important advantage attained by reason of the described construction is that the angle of aileron or flap movement required in effecting the usual airplane control is comparatively small due to the fact that the lift changes much more movement when no convex discontinuities are produced by the flap movement.

.Another advantage obtained by the invention follows from the shift of the airfoil zero lift line upon movement-of the flap within the low drag range, whereby the flap may-be employed to shift the zero lift setting of the wing relative to the fuselage and landing gear without an accompanying appreciable increase in drag. It will be apparent that this is of great advantage in connection with take of! maneuvers. Also, such change in zero lift setting is relative to the stabilizer, and therefore may be employed as a longitudinal trimming device without appreciable change in drag. Another feature of the invention follows from the shift of the center of pressure of the wing accompanying changes in effective camber upon movements of the flap. Thus the center of pressure may be adjusted to the center of gravity thout appreciable change in drag, thus reducing loads on the tail or other stabilizing surfaces.

Although it is well known that airfoils having curved median lines provide greater maximum lifts in conjunction with flaps than do symmetrical airfoils, the use of curved median line airfoils has heretofore been attended by high drags and excessive tail loads due to wide center of pressure variations. My invention, however, by providing camber and center of pressure control without appreciable change in section drag, permits the use of curved median line main airfoils without the previously attendant increased tail load and without appreciable increase in section drag over that of an equivalent symmetrical type airfoil.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope, of the invention which is defined in the appended claims.

I claim: 1. In an airplane, a fuselage, a main sustaining wing including a main section having upper and lower surfaces and supported upon said fuelage,

a trailing section having upper and lower surfaces, and means mounting said trailing section in contiguousrelation with the trailing edge of said, main section and for angular movement relative thereto for operation as an aileron and as a lift and drag varying flap, the respective extended contours of the upper and lower surfaces of said tra ling section intersecting the respective extended contours of the upper and lower surfaces of said main section in the region of said contiguous relation, the included angles between the upper and lower surfaces of said main section and said trailing section respectively at the region of said contiguous relation being such that the sum of the external angles between said surfaces at said re gion of contiguous relation is substantially less than-360 degrees, the range of said aileron operation including a substantial range of angular movement throughout which neither of said external angles exceeds 180 degrees and a substantial range of angular movement throughout-which the lower of said external angles exceeds 180 degrees,

- the range of said flap operation including a substantial range of angular movement throughout which neither of said external angles exceeds 180 degrees and a substantial range of angular movement throughout which the upper of said external angles exceeds 180 degrees. 2. In an airplane, a fuselage, a main sustaining wing including'a main section having upper and lower surfaces and supported upon said fuselage, a trailing section having upper and lower surfaces, and means mounting said trailing section incontiguous relation with the trailing edge of said main section and for angular move ment relative thereto for operation as an aileron and as a lift and drag varying flap, the respective extended contours of the upper'and lower surfaces of said trailing section intersecting the respective, extended contours of the upper and lower surfaces of said main section in the region of said contiguous relation, the included angles between the upper and lower surfaces of said main section and said trailing section respectively at the region of said contiguous relation being such that the sum of the external angles between said surfaces at said region of contiguous relation is substantially less than 360 degrees, the range of said aileron operation including a substantial range of angular movement throughout which neither of said external angles exceeds 180 degrees, the range of said flap operation including a substantial range of. angular movement throughout which neither of said external angles exceeds 180 degrees.

3. In an airplane, a fuselage, a main sustaining wing including a main section having upper and lower surfaces and supported upon said fuselage, a movable section having upper and lower surfaces, and means mounting said movable section in contiguous relation with the trailing edge of said main section and for angular movement relative thereto for operation as a lift and drag varying flap, the respective extended contours of the upper and lower surfaces of said movable section intersecting the respective extended contours ;of the upper and lower surfaces of said main section in the region of said contiguous relation, the included angles between the upper and lower surfaces of said main section and said movable section respectively at the region of said contiguous relation being such that the sum of the external angles between said surfaces at said region of contiguous relation is substantially less than 360 degrees.

tiguous relation with the trailing edgeof said main section and for angular movement relative thereto, the respective extended contours of the upper and lower surfaces of said trailing section intersecting the respective extended contours of the upper and lower surfaces of said main section in the region of said contiguous relation, the included .angles between the upper and lower surfaces of said main section and said trailing section respectively at the region of said contiguous relation being such that the sum of the external angles between said surfaces at said region of contiguous relation is substantially less than 360 degrees.

5. In an airplane, a fuselage, a main sustaining wing including a main section having upper and lower surfaces and supported upon said fuselage, a trailing section having upper and lower surfaces, andrneans mounting said trailing section in contiguous relation with the trailing edge of said main section and for angular movement rel- '50 4. In an airplane, a fuselage, a. main sustaining gig,

ative thereto, the respective extended contours of the upper and iowersurfaces of said trailing section intersecting the respective extended contours of the upper and lower surfaces of said main section in the region of said contiguous relation, the inciuded angles between the upper and lower surfaces of said main section and said trailing section respectively at the region of said contiguous relationbeing such that the sum of the external angles between'said surfaces at said region of contiguous relation is substantially less than 360 degrees, said trailing section being movable within a substantial range of angular movement throughout which range neither of said external angles exceeds 380 degrees.

6. In an airplane, a fuselage, an airfoil including, a main section havingupper and lower surfaces and a curved median line and supported extended contours of the upper and lower surfaces of said main section in the region of said contiguous relation, the included angles between the upper and lower surfaces of said main section and said trailing section respectively at the region of said the sum of the external angles between said surfaces at said region of contiguous relation is substantially less than 360 degrees, said trailing section being movable within a range of angular movement including a position wherein one of said external angles exceeds 180 degrees.

7. In an airplane, a fuselage, an airfoil ineluding a main section having upper and lower a curved median line and supported upon said fuselage, a trailing section having upper and lower surfaces, and means mounting said trailing section in contiguous relation with the trailing edge of said main section and for angular movement relative thereto, the respective extended contours of the upper and lower surfaces of said trailing section intersecting the respective extended contours of the upper and lower surnot exceed 352 main section in the region of said contiguous relation, the included anglesbetween the upper and lower surfaces of said main section and said trailing section respectively atthe reof'contiguous relation does degrees, said trailing section being movable in a range angular movement throughout which neither of said external angles exceeds IBO-degrees:

8. In an airplane, a fuselage, an airfoil including a main section having faces and a curved median line and supported upon said fuselage, a trailing section having upfacesat said region of grees.

contiguous relation being such that the upper and lower surfaces of said main section 1 and said trailing section respectively at the region of said contiguous relation being such that the sum of the external angles between said surcontiguous relation is substantially less than 360 degrees, said trailing section being movable within a substantial range movement throughout which range neither of said external angles exceeds 180 de- 9. In an airplane, a fuselage, an airfoil including a main section having upper and lower surfaces and a curved median line and supported upon said fuselage. a trailing section having upper and lower surfaces, and means mounting said trailing section in contiguous relation with the trailing edge of said main section and for angular movement relative thereto, the respective exsaid trailing, section and the lower surface of said trailing section coincides with a continuation of the lower surface of said main section at a second angular position which is substantially removed from said first angular position.

10. In an airplane, a fuselage, an airfoil including a main section having upper and lower surfaces and'a curved median line and supported upon said fuselage, a trailing section having upper and lower surfaces, and means mounting said trailing section in contiguous relation with the trailing edge of said main section and forangular movement relative thereto, the respective extended contours of the upper and lower surfaces of said'trailing section intersecting therespective extended contours of the upper and lower surfaces of said main section in the region of said contiguous relation, the included angles between upper and lower surfaces of said main section and said trailing section respectively at the region of said contiguous sum of the external relation'being such that the angles between said surfaces,

at said region of contiguous relation is substan" tially less than 360 degrees,

JOSEPH M. Gwnm, JR. 

